Article comprising a superconducting RF filter

Abstract

The disclosed superconducting multipole RF filter comprises a multiplicity of coupled circular disk resonators designed for operation in the TM 010 mode. The disk resonators are arranged in a co-axial stack, with a circular metal spacer sandwiched between any two neighboring disk resonators. Each metal spacer has a central through-aperture, with a conductive member disposed in the through-aperture and electrically connecting the two neighboring disk resonators that are sandwiching a given metal spacer. A disk resonator comprises two circular members, each circular member comprising a circular dielectric substrate, exemplarily a LaAlO 3 wafer. Superconducting layers (typically YBCO) are disposed on each major surface of the substrate. The two members are joined together such that conductive layers (typically gold) electrically connect the two outside superconducting layers. The disclosed RF filter has good power handling capability, is compact, has good heat removal and relatively simple tuning. It can, for instance, be advantageously used as transmit filter in base stations of a wireless communication system.

What is claimed is: 
     
       1. An article comprising a RF filter comprising a multiplicity of coupled circular disk resonators selected for operation in a resonator mode that has substantially no azimuthal current flow, and further comprising an input contact for providing a RF input current to the filter and an output contact for receiving a RF output current from the filter; CHARACTERIZED IN THAT said disk resonators are arranged in a coaxial stack, with a circular metal spacer sandwiched between any two neighboring disk resonators, any given said metal spacer having a central through-aperture, with a conductive member disposed in said through-aperture and electrically connecting said two neighboring disk resonators that are sandwiching said given metal spacer.     
     
     
       2. Article according to claim 1, wherein a given one of said disk resonators comprises two circular members, a given one of said circular members comprising a circular dielectric substrate having superconductive material disposed on a first and a second major surface of said dielectric substrate, said dielectric substrate also having a circumferential surface substantially without superconductive material disposed thereon, said two circular members jointed together such that the respective first major surfaces are facing each other, and such that the superconducting materials on the respective second major surfaces are electrically connected. 
     
     
       3. Article according to claim 2, wherein the superconducting material disposed on the second major surface comprises a ring-shaped outer portion and a central circular patch that is separated from the ring-shaped outer portion by a circular trench extending through the superconducting material to the substrate, and wherein the superconducting material disposed on the first major surface comprises a circular layer having a diameter that is less than a diameter of said dielectric substrate, such that a ring-shaped portion of said first major surface is not covered by the superconducting material. 
     
     
       4. Article according to claim 3, wherein on the circumferential surface of the circular dielectric substrate is disposed a non-superconducting metal layer extending onto said first major surface without contacting the superconductive material on the first major surface, and extending onto said second major surface and contacting the ring-shaped outer portion of the superconducting material on the second major surface, such that the ring-shaped outer portions of the superconducting material on the respective second major surfaces of the two circular members of the given disk resonator are electrically connected. 
     
     
       5. Article according to claim 1, wherein said given metal spacer comprises titanium. 
     
     
       6. Article according to claim 2, wherein said superconductive material is YBa 2  Cu 3  O x , where x is about 6.9. 
     
     
       7. Article according to claim 1, further comprising at least one elastic member selected to apply an axial force on the coaxial stack. 
     
     
       8. Article according to claim 2, wherein said circular dielectric substrate comprises a ferrimagnetic oxide, and wherein said article further comprises magnetic field generating means adapted for providing a DC magnetic field to said ferrimagnetic oxide. 
     
     
       9. Article according to claim 1, wherein the article is a communication system comprising a source of signals to be transmitted, a power amplifier connected to said source and having an amplifier output, a filter that receives said amplifier output and has a filter output, an antenna that receives said filter output and radiates electromagnetic radiation representative of the filter output, wherein said filter is a filter according to claim 1.